You face three doors. Behind one is freedom, behind the others are tigers. Three guards stand before the doors. One always tells the truth, one always lies, and one answers randomly. You can ask one guard one yes/no question. What do you ask?
Hints
Ask a question that creates a logical loop forcing two guards to agree.
Answer
Ask any guard: 'If I asked you whether the middle door leads to freedom, would you say yes?' Then ask a different guard the same question. The door where two guards agree (or disagree in a pattern) is safe.